Process for machining a flexible foam

ABSTRACT

The invention relates to a process for machining a flexible foam. The flexible foam is treated to temporarily harden the foam. The hardened foam is machined. The foam is then returned to its original flexible state.

BACKGROUND OF THE INVENTION

[0001] This invention relates in general to machining processes, and inparticular to a process for machining a flexible foam.

[0002] Flexible foams such as polyurethane foams are used in manydifferent commercial applications. In a typical application the flexiblefoams are used for padding. For example, the flexible foams can beformed into the shape of foam pads for vehicle seats.

[0003] Flexible foams are usually molded into a desired shape. However,in some situations it would be advantageous to be able to machine aflexible foam to create a desired shape, for example, to produceprototype foam pads for vehicle seats. Unfortunately, a flexible foamsuch as a polyurethane foam is very difficult to machine due to itsflexible nature. The cutting tools of conventional automated cuttingequipment catch and tear the foam instead of cutting it. As a result, itis a common practice to cut the flexible foam by hand instead of usingautomated equipment such as a CNC milling machine, even when CADD datais available to produce cutter paths for the automated equipment.Cutting by hand is slower and not as accurate as cutting with automatedequipment.

[0004] U.S. Pat. No. 6,273,697 B1 to Harfmann, issued Aug. 14, 2001,discloses a process for forming a low-density polymer foam article inwhich a blowing agent and a resin are combined to form a mixture, andthe mixture is cooled to a temperature approaching its freezing pointand then extruded. The extruded foam is then cooled by direct contactwith a cooling surface. In the embodiment shown in FIG. 1, a knife isused to slit the foam to create a sheet, which is then wound into rolls.There is no suggestion in this patent to start with a flexible foam, andthen to treat the flexible foam to temporarily harden it before cutting.The patent discloses a rigid foam used to make an article such as a foodcontainer, not a flexible foam adapted for use as padding or the like.Moreover, the disclosed process cools the foam to condense the blowingagent, not to harden the foam to make it easier to cut.

SUMMARY OF THE INVENTION

[0005] This invention relates to a process for machining a flexiblefoam. The flexible foam is treated to temporarily harden the foam. In apreferred embodiment, the flexible foam is treated by cooling theflexible foam, such as by applying a liquefied gas to the flexible foam,or by soaking the flexible foam with water and then freezing the water.The hardened foam is machined such as by cutting it into a desiredshape. The foam is then returned to its original flexible state.

[0006] Various objects and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the preferred embodiments, when read in light of theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a side elevational view, partly in cross-section,showing a flexible foam being cooled to temporarily harden the foam, anda cutting blade of an automated cutting equipment cutting the hardenedfoam.

[0008]FIG. 2 is a perspective view of a foam pad for a vehicle seat thatcan be produced using the process of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0009] The process of the invention overcomes the previous difficultiesin machining flexible foams. The process allows the cutting tools ofconventional automated cutting equipment to cleanly cut the flexiblefoams instead of catching and tearing the foams. The use of automatedequipment such as a CNC machine will significantly increase the speedand accuracy of producing articles such as prototype foam pads forvehicle seats.

[0010] The process can be used to machine any type of flexible foam. By“flexible” is meant a foam which is soft and easily bendable,stretchable and compressible by hand. The invention is not intended toapply to a rigid foam such as a polystyrene foam or the rigid polymerfoams disclosed in the above-described Harfmann patent. The foam isflexible at room temperature (72° F.). The foam is generally a low- ormedium-density, open-celled foam. In a preferred embodiment, theflexible foam is a polyurethane foam.

[0011] The flexible foam is treated to temporarily harden the foam. Anysuitable method can be used to harden the foam such that it can bemachined with a conventional machining tool such as a cutting tool. Theentire foam piece can be hardened, or just the portion of the foam inthe path of the machining tool can be hardened. Preferably, the flexiblefoam is treated by cooling the flexible foam in order to temporarilyharden the foam. The flexible foam is preferably cooled to a temperatureof about 32° F. or below.

[0012] In one embodiment of the invention, the flexible foam is cooledby soaking the foam with a liquid and then freezing the liquid.Typically, the liquid used is water, although other liquids havingfreezing points within a practicable range can also be used. Theflexible foam can be soaked with the liquid in any suitable manner, suchas by pouring or spraying the liquid onto the foam until the foam iscompletely soaked, or by immersing the foam in a container of theliquid. Preferably, the size and shape of the container are similar tothat of the foam piece, and the foam is removed from the container formachining after freezing the liquid. The liquid can be frozen by coolingin any suitable manner.

[0013] In another embodiment of the invention, the flexible foam iscooled by applying a liquefied gas to the flexible foam. As theliquefied gas evaporates, it cools and hardens the foam. Any suitableliquefied gas can be used, such as liquid nitrogen or liquid carbondioxide. The liquefied gas can be applied to the flexible foam in anysuitable manner, such as by pouring, spraying or immersion. Typically,the liquefied gas is applied by spraying. In one embodiment, theliquefied gas is applied only to the portion of the flexible foam thatis in the path of the machining tool.

[0014] The foam is machined after it has been temporarily hardened. Anysuitable machining equipment can be used, such as cutting, milling ordrilling equipment. Preferably, the hardened foam is cut using automatedcutting equipment, and more preferably using a CNC machine.

[0015]FIG. 1 shows a process for machining a flexible foam according tothe invention. A flexible foam 10 is positioned on the bed 12 of anautomated cutting machine. The cutting tool 14 of the machine includes ahousing 16, a cutting head 18 mounted in the housing 16, and a cuttingblade 20 attached to the end of the cutting head 18. The cutting head 18moves up and down so that the cutting blade 20 cuts the flexible foam10. The housing 16 can move in any direction laterally relative to theflexible foam 10 to allow the cutting blade 20 to cut a desired path inthe foam. In the drawing, the housing 16 and cutting blade 20 are shownmoving to the left to cut a path 22 in the foam 10. A spraying apparatus24 is mounted on the housing 16 for spraying a liquefied gas 26 on theflexible foam 10. The liquefied gas 26 temporarily hardens the foam 10so that it can be easily cut with the cutting blade 20. The sprayingapparatus 24 includes a spraying head 28, and a nozzle 30 on the end ofthe spraying head 28 through which the liquefied gas 26 is sprayed. Thespraying apparatus 24 also includes a first motor 32 that causes thespraying head 28 to rotate clockwise or counterclockwise, and a secondmotor 34 that causes the spraying head 28 to move in or out of the planeof the drawing. The motors 32 and 34 allow the spraying head 28 to bepositioned to spray the liquefied gas 26 in the path of the cuttingblade 20 even when the blade changes directions. The spraying apparatus24 includes a gas supply 36 and a flow control mechanism 38. Although aspecific apparatus is shown in the drawing, it is understand that anysuitable apparatus can be used in the process. FIG. 2 shows a foam pad40 for a vehicle seat that can be produced using the process of theinvention.

[0016] After the foam has been machined, the foam is allowed or causedto return to its original flexible state. This typically involvesapplying heat to the foam or allowing the foam to heat slowly at roomtemperature. The foam can be dried if necessary.

[0017] In accordance with the provisions of the patent statutes, theprinciple and mode of operation of this invention have been explainedand illustrated in its preferred embodiments. However, it must beunderstood that this invention may be practiced otherwise than asspecifically explained and illustrated without departing from its spiritor scope.

What is claimed is:
 1. A process for machining a flexible foamcomprising the steps of: treating the flexible foam to temporarilyharden the foam; machining the hardened foam; and then returning thefoam to its original flexible state.
 2. A process according to claim 1wherein the flexible foam is treated by cooling the flexible foam.
 3. Aprocess according to claim 2 wherein the flexible foam is cooled to atemperature of about 32° F. or below.
 4. A process according to claim 2wherein the flexible foam is cooled by applying a liquefied gas to theflexible foam.
 5. A process according to claim 4 wherein the liquefiedgas is applied by spraying.
 6. A process according to claim 4 whereinthe liquefied gas is liquid nitrogen or liquid carbon dioxide.
 7. Aprocess according to claim 4 wherein the liquefied gas is applied onlyto a portion of the flexible foam to be machined.
 8. A process accordingto claim 7 wherein the foam is machined with a cutting tool that movesrelative to the foam, and wherein the liquefied gas is applied byspraying it from a nozzle mounted directly in front of the cutting tool.9. A process according to claim 2 wherein the flexible foam is cooled bysoaking the flexible foam with a liquid and then freezing the liquid.10. A process according to claim 9 wherein the liquid is water.
 11. Aprocess according to claim 1 wherein the flexible foam is a polyurethanefoam.
 12. A process according to claim 1 wherein hardened foam ismachined by cutting.
 13. A process according to claim 12 wherein thehardened foam is cut using automated cutting equipment.
 14. A processaccording to claim 13 wherein the hardened foam is cut using a CNCmachine.
 15. A process according to claim 12 wherein the hardened foamis cut into the shape of a foam pad for a vehicle seat.
 16. A processfor machining a flexible foam comprising the steps of: cooling theflexible foam by applying a liquefied gas to the flexible foam, in orderto temporarily harden the foam; cutting the hardened foam usingautomated cutting equipment; and then returning the foam to its originalflexible state.
 17. A process according to claim 16 wherein the flexiblefoam is a polyurethane foam.
 18. A process according to claim 16 whereinthe foam is cut using a CNC machine.
 19. A process for machining aflexible foam comprising the steps of: cooling the flexible foam bysoaking the flexible foam with a liquid and then freezing the liquid, inorder to temporarily harden the foam; cutting the hardened foam usingautomated cutting equipment; and then returning the foam to its originalflexible state.
 20. A process according to claim 19 wherein the flexiblefoam is a polyurethane foam.